Process for spinning cellulosic fibers



Nov. 14, 1967 N. DRiSCH ET AL 3,352,957

PROCESS FOR SPINNING CELLULOSIC FIBERS Filed Nov. 4, 1963 UMPERATUPE "c JP/NN/NG BATH CONTAINING 259/] M A/11 504 A/VD /29 /Z 0F SULPHUR/C ACID 2/750 0 /1 Z0304 0.39/2 X Z0504 OJg/Z lr lvenlor g NIL-OLA a bmsa Au L EP BFMH y A ltorney United States Patent 3,352,957 PROCESS FOR SPINNING CELLULOSIC FIBERS Nicolas Drisch and Paul Herrbach, Paris, France, assign ore to Chimiotex S.A., Geneva, Switzerland, a corporaration of Switzerland Filed Nov. 4, 1963, Ser. No. 321,063 Claims priority, application France, Nov. 6, 1962, 914,533; Dec. 12, 1962, 917,772 5 Claims. (Cl. 264-496) According to the present invention, filaments having improved characteristics are obtained, notably filaments of high tenacity both in the conditioned state and in the wet state, by spinning viscose as described in French Patent No. 1,266,492 into a bath of low acid content, the essential element of the invention being that this first bath is maintained, not at ambient temperature, but at an extremely low temperature, below C., and not-ably between 10 C. and 0 C.

It is known that dilute acid baths at ambient temperature have essentially a coagulating action on freshly spun filaments, and only a slight regenerating action. Under these conditions, the filaments formed have a high gamma index and they can be highly stretched between the first coagulating bath and the second regenerating bath.

The process according to the invention makes it possible to obtain a high stretching capacity by physical means, namely the use of very low bath temperatures, whereby their regeneration power is further increased and very high gamma indices can thus be obtained. In the stretching, it has been found (and other elements) that with a cold bath and a low acid concentration, the possible, degree of stretching of the gel is higher in proportion as the zinc sulphate content of the bath is lower. With the same temperature and the same zinc sulphate content, it is possible to stretch the gel to a greater extent as the sodium sulphate concentration of the bath is lower.

For example, in the case of a viscose containing 5.5% of cellulose and 3.2% of sodium hydroxide, viscosity 600 poises, a DR of 600, and a gamma index of 67 spun into a weakly acid bath, the gamma indices indicated in Tables I and II have been found as a function of temperature:

TABLE I.BATH CONTAINING g. OF SULPHURIO ACID,

50 g. OF NazSO4 AND 0.3 g. OF ZnSO; PER LITRE Temperature 17 C. 14 0. 8 0. 5 0. 2 0.

Gamma index on leaving the first bath 42 45 48 52 54 Gamma index at the end of the stretching 20 23 26 27 30 TABLE IL-BATH CONTAINING 12 g. OF SULPHURIC ACID, g. OF NazSOr AND 0.3 g. OF ZnSOr PER LITRE Temperature 17 C. 14 0. 8 0. 5 0. 3 C.

Gamma index on leaving the first bath 40 42 47 49 53 Gamma index at the end of the stretching 20 22 28 29 31 3,352,957 Patented Nov. 14, 1967 In fact, spinning tests with the same viscose in baths having different sulphate contents have shown that the possible degree of stretch of the filaments in gel form increases rapidly when the zinc sulphate content and the sodium sulphate content of the bath are reduced. This increase in the degree of stretch is clearly illustrated by the accompanying FIGURE 1, in which the percentages of stretch have been plotted along the ordinates and the centigrade temperatures along the abscissae.

It is found that for each bath formula the points obtained are located on curves whose inclination is more pronounced as the zinc sulphate content is lower. In addition, the curves corresponding to baths containing 25 g./l. of Na SO are on a higher level than the curves corresponding to baths containing 50 g./l. of Na SO When a concentration of 0.7 g. litre of ZnSO, is reached with a constant sodium sulphate concentration, the temperature reduction affords no further advantage.

In putting the invention into practice, there is preferably employed a viscose containing at least 3% of cellulose and 1.59% of sodium hydroxide, and of which the carbon disulphide content is at least 35% based upon the alpha-cellulose employed. The gamma index of the viscose at the time of the spinning must be between 45 and and the cellulose contained in the viscose must have a DR of at least 400, and preferably above 500. The viscosity of the viscose must be between and 1000 poises, and it is preferably higher than 400 poises. The viscose, which contains in addition 0.1-5% of a surface-active protecting agent such as sodium oleate, for example (based upon the alpha-cellulose) is spun into a bath which contains less than 40 g./l. of acid, preferably from 5 to 25 g. of acid per litre, from 10 to 100 g. per litre of sodium sulphate, preferably less than 40 g./l., and little or no zinc sulphate (less than 1 g./litre). Although zinc sulphate tends to reduce the possible degrees of stretch, it is nevertheless preferable to use small quantities thereof because under these conditions a fibre of better quality is obtained. The temperature of the bath is extremely low and is below 10 C., preferably between 10 and 0 C. In addition, formaldehyde may be incorporated in the bath, or small quantities of retarding agents such as N-methylcyclohexylamine, polyhydroxyalkylamines, ethylene polyoxides, etc., may be added to this bath.

After leaving the first bath, the excess solution is rea slight reduction in tension through a third degassing bath consisting of hot dilute acid. They are finally re-' ceived on an appropriate support without tension. After a relaxation period of several hours, the filaments are cut in the acid state in order to produce dis-' continuously fibres, these fibres are washed and they are treated in order to improve their transverse characteristics and their dye aflinity.

The filaments which are produced by the process described possess the so-called Polynosic structure, which means that their structural characteristics are stable and are not appreciably modified by a subsequent treatment with 5% sodium hydroxide, while under the same conditions filaments of ordinary rayon and pneumatic tire rayon are thoroughly disorganized. The filaments according to the invention have a high tenacity which exceeds 4 g./den. in the wet state and 4.5 g./ den. in the conditioned state and they possess a high modulus of elasticity in the wet state, which results in a wet elongation of less than 3% under a load of 0.5 g./den. They have a circular cross-section and their swelling is currently lower than 65%. On appropriate treatment with 70% (by weight) nitric acid, it can be seen that they possess a very characteristic fibrillar structure which is much more similar to that of cotton than to that of other regenerated cellulose fibres. Physical tests, such as, for example, the X-ray diffraction and birefringence ests, reveal the existence of an extremely oriented structure, but with good transverse properties.

There will now be described three examples of the application of the process of the invention, it being understood that these examples have no limiting character and that they cover any variant in the same spirit. Thus, the invention is also applicable to the manufacture of other articles of regenerated cellulose such as textile rayon, high-tenacity rayon, films, etc.

Example 1.A cellulose pulp having a high alpha-cellulose content is immersed for 30 minutes in sodium hydroxide in a proportion of 242 g./l., at a temperature of 22 C., and thereafter pressed to a proportion of 3.13 in relation to the alpha-cellulose. The alpha-cellulose formed is not subjected to any ripening and there is directly added thereto 43% of carbon disulphide (based on the alpha-cellulose). The xanthate formed is thereafter dissolved in dilute sodium hydroxide at low temperature, but there is added to the mass an additional quantity of 5% of carbon disulphide together with 2% of sodium oleate and also 0.25% of Intrasol FSW (the condensation product of a fatty alcohol with ethylene oxide) and 0.15% of Nonanol, an alcohol with nine carbon atoms and a primary alcohol group (based on the alpha-cellulose).

There is thus obtained a viscose containing 5.5% of cellulose and 3.2% of sodium hydroxide, of which the characteristics are: DP 600, viscosity 600 poises, gamma index 67.

The viscose is spun with the aid of a spinneret having 8000 holes of .06 mm. diameter and a tube 5 cm. in diameter and 20 cm. long, into a first bath containing 12 g. of sulphuric acid, 25 g. of sodium sulphate and 0.3 g. of zinc sulphate per litre, as also small quantities of Ceponol TS (a dodecal toluene sulfonate) at a temperature of 8 C. The rate of flow is adjusted to produce filaments of 1.5 den. after the stretching operations. After a first passage of 83 cm., the filaments are extracted from the bath, freed from excess solution by compression between the two rollers, and stretched in air by 160%. The gamma index of the filaments leaving the first bath is 45.7 and it falls to 28 at the end of the stretching. The filaments thereafter pass, through a second bath of the same composition and at the same temperature as the first bath, the length of immersion being 230 cm., and they then enter a third degassing bath at a temperature of 95 C., obtained by dilution of the first bath so that its sulphuric acid content is between 6 and 8 g. per litre, the sodium sulphate and the zinc sulphate being diluted in the same ratio. The length of travel through this bath is 490 cm. and the filaments undergo therein a detensioning of 0. 8%. There is received in the pot the tow of 12,000 den., at a final speed of 12.5 metres per minute. After standing for a number of hours, the tow is divided in the acid state. The fibres formed are then deacidified by washing with softened water, and are treated with a sodium hydroxide solution in a concentration of 40 g./l. at 30 C. for 30 minutes, in the state of primary swelling and then subjected to rinsing, desulphur-ising, washing, sizing and drying operations. The characteristics of the filaments obtained are indicated in Table III as compared with those of filaments spun under the same conditions, but into baths at ambient temperature (20 C.).

TABLE III Filaments Filaments obtained according with a bath to the at 20 C. invention Count, den. l. 5 1. 5 Dry tenacity, g./dcn 3. 8 5. 2 Wet tenacity, g./den 2. 9 4. 1 Dry elongation, percent 13 12. 3 Wet elongation, percent 14 12. 9 Loop tenacity, g./dcn 0. 6 0.7 Modulus (wot elongation, percent under a load of 0.5 g./den.) 2.3 1. 6 So ca1led polynosic properties: Wet tenacity after action of 5% NaOH in gJden 2 3.2 Modulus (wet elongation, percent under a load of 0.5 gJden.) alter the action of 5% Na-OEL. 7 3.7

This table clearly shows that the filaments according to the invention possess so-called Polynosic properties in a distinctly higher degree than ordinary filaments spun into a bath at 20 C.

A fabric of a texture of 47 x 27 woven with yarns having a metric count of 70, themselves obtained from filaments according to the invention shows a warp abrasion (on the Stoll-Flex apparatus) of 2700, in contrast to an abrasion of 1460 in the case of a similar fabric based on known filaments (spun into a bath at 20 C. under otherwise equal conditions).

Example 2.-A viscose containing 5.5% of cellulose and 3.2% sodium hydroxide, prepared in the same way as that indicated in Example 1 is spun with the aid of the same tube arrangement into a first bath containing 12 g.- of sulphuric acid and 26 g. of sodium sulphate per litre, but completely free from zinc sulphate, at a temperature of 3 C. After a passage of 100 cm. the filaments are extracted from the bath, are freed from sulphur solution between two compression rollers and are stretched in air by 230 C. The gamma index of the filaments is 53 when they leave the first bath and 31 at the end of the primary stretch. The filaments thereafter pass through a second bath of the same composition and at the same temperature as the first, the length of immersion being 230 cm., and then through a third degassing bath at a temperature of C. obtained by dilution of the first bath, so that the sulphuric acid content is between 6 and 8 g. per litre, the sodium sulphate having the same dilution ratio. The length of passage through this bath is 550 cm. and the filaments undergo therein a detensioning of 1.5%. There is received in the pot a tow of 12,000 den. at a speed of 12.8 metres per minute. The finishing operation and notably the sodium hydroxide treatment are carried out as in Example 1. Filaments are obtained which have the following characteristics:

Count, den. 1.5 Dry tenacity, g./den. 5.8 Wet tenacity, g./ den. 5.0 Dry elongation, percent 12.0 Wet elongation, percent 12.5 Loop tenacity, g./den. 0.6 Modulus (wet elongation percent under a load of 0.5 g./den.) 1.8

Example 3.A pulp of linters is immersed for 35 minutes in sodium hydroxide in a concentration of 240 g. per litre at a temperature of 20 C., and the alkali cellulose obtained is pressed to a proportion of 3.1 in relation to the alpha-cellulose. The alkali cellulose is thereafter ground and then treated without any ripening with 44% of carbon disulphide (calculated on the alpha-cellulose). The xanthate formed is dissolved in cold sodium hydroxide, while there are incorporated at the same time 0.6% of Ceponol and small quantities of surface-active products. Finally, there is added a further quantity of 5% of carbon disulphide. The viscose obtained contains 6% of cellulose and 4% of sodium hydroxide. Its DP is 600, its viscosity 650 poises and its gamma index 67.

Spinning is effected as in Example 1 with the aid of an 8000-hole spinneret and with a tube 5 cm. in diameter and 20 cm. long into a bath containing 16 g. of sulphuric acid, 52 g. of sodium sulphate and 0.3 g. of zinc sulphate per litre, at a temperature of 3 C. The filaments formed travel a distance of 90 cm. through the bath, whereafter they are extracted therefrom, freed from the excess solution by which they are impregnated by passing them between two compression rollers, and are stretched by 215% during their travel through the air between the first and second baths. The gamma index is 53 at discharge from the first bath and still amounts to 31 at the end of the stretching. The filaments thereafter pass through a second bath having the same composition and at the same temperature as the first, the length of travel being 230 cm., and then through a third degassing bath at a temperature of 95 C., obtained by dilution of the first bath, so that its sulphuric acid content is between 6 and 8 g. per litre, the sodium sulphate and the zinc sulphate being in the same dilution ratio. The length of travel through the third bath is 550 cm. and the filaments undergo therein a detensioning of 1.5%. The tow of 12,000 den. is received in the pot at a speed of 12.5 metres per minute. The finishing operations and notably the treatment with sodium hydroxide are carried out as in Example 1. Filaments are obtained which have the following characteristics:

Owing to the increase of the Na SO concentration, the values obtained in this third example are in fact below those of Example 2.

In a further embodiment of the invention the filaments derived from the first bath may be passed through a cold intermediate bath containing an aldehyde and then stretched in a second bath, preferably cold, which also contains an aldehyde. The presence of the aldehyde results in the formation of a more stable complex of xanthate and the lowering of the gamma index of the filaments in the gel form is very rapidly blocked at a relatively short distance after it leaves the first bath.

Consequently, the filaments have an even higher gamma index during the stretching operation in addition this index falls much more slowly.

It has also been found that filaments stretched in air may undergo a further stretch in a cold secondary bath, in contrast to the usual practice, which consists in using a hot second bath. Under these conditions, it is possible to reach substantially greater stretches, and consequently exceptional tenacities.

The use of a cold intermediate bath and of a cold second bath, both containing an aldehyde, is extremely advantageous because it avoids the evolution of noxious vapors in the atmosphere. Moreover, this procedure avoids contamination of the first spinning bath, because when the aldehyde, for example formaldehyde, is in contact with hydrogen sulphide, or thiocarbonates, as is the case the first bath, trithiane is formed, which disturbs the normal course of the spinning and necessitates continuous purification of the first bath.

Use is made of a viscose containing at least 3% of cellulose and 1.5-9% of sodium hydroxide, the percentage of carbon disulphide added being 35% at least calculated on the alpha-cellulose employed. The gamma index of the viscose at the time of spinning being between 45 and 100 and the cellulose contained in the viscose having a DP of at least 400, preferably higher than 500, the viscosity of the viscose being between 150 and 1000 poises,

and preferably higher than 400 poises. This viscose is spun into a first bath which contains at least 40 g. of acid, preferably from 5 g. to 25 g. of acid per liter, from 10 g. to g., preferably less than 40 g., per litre of sodium sulphate, and less than 1 g. per litre zinc sulphate. The bath may contain in addition small quantities of a modifying agent such as an ethylene polyhydroxide, or an amine. The temperature of the first bath is extremely low and is between 0 and 10 C., preferably between 2 and 8 C.

After leaving the first bath, the filaments are freed from surplus solution by squeezing between rollers and they thereafter pass around a roller which is partially immersed in a cold intermediate bath containing formaldehyde, which bath may have, apart from the aldehyde, the same composition and the same temperature as the first bath. The filaments are thereafter stretched -by at least while travelling through air, and again by at least 20% in a second cold dilute acid bath containing an aldehyde, which second bath may have the same composition and. the same temperature as the intermediate bath. Finally, the filaments are subjected to a regenerating treatment in a third bath, under slight detensioning, and they are received in pots. After a period of relaxation of a number of hours the filaments in the acid state are cut to produce discontinuous fibres, and these fibres are washed and given a primary swelling treatment with 5% sodium hydroxide in order to improve their transverse characteristics and their affinity.

The filaments produced by the described process possess the so-called Polynosic structure and their charac teristics are stable and only slightly modified by a subsequent treatment with 5% sodium hydroxide, while under the same conditions ordinary rayon filaments and rayon filaments for pneumatic tires are thoroughly disorganized. These filaments have a high tenacity which exceeds 4 g./den. in the wet state and 4.5 g./den. in the conditioned state and they possess a high modulus of elasticity in the wet state, which results in an elongation of less than 3% under a load of 0.5 g./den. They have a circular crosssection and their swelling is currently below 65%. By means of an appropriate treatment in 70% (by weight) nitric acid, it can be shown that they possess a very characteristic fibrillar structure which resembles cotton. Physical tests, such as X-ray diffraction and birefringence tests, reveal the existence of an extremely oriented structure with, however, good transverse characteristics.

Example 4.-In a first embodiment a cellulose pulp having a high alpha-cellulose content is immersed for 30 minutes in sodium hydroxide in a concentration of 242 g./litre, at a temperature of 22 C., and is thereafter pressed to a proportion of 3.1 calculated on the alphacellulose. The alkali cellulose formed is not subjected to any ripening and 43% of carbon disulphide are directly added thereto (calculated on the alpha-cellulose). The xanthate formed is thereafter dissolved in dilute sodium hydroxide at low temperature, while there is added to the mass an additional quantity of 5% of carbon disulphide, simultaneously with 0.25% of Intrasol FSW, and 0.15% of Nonanol (calculated on the alpha-cellulose).

In this way, there is obtained a viscose containing 5.5%

of cellulose and 3.2% of sodium hydroxide, of which the characteristics are: DP 600, viscosity 600 poises, gamma index 65.

The viscose is spun with the aid of a spinneret having 8000 holes of mm., and with a tube 5 cm. in diameter and 20 cm. long into a first bath containing 15 g. of sulphuric acid, 25 g. of sodium sulphate and 0.3 g. of zinc sulphate per litre, as also small quantities of Ceponol TS, at a temperature of 8 C. After travelling a distance of 83 cm., the filaments are extracted from the bath and are freed from surplus solution between two pressure rolls, and they pass around a roller which is partially immersed in an intermediate bath at 80 C., having the same composition as the first bath, but containing in 7 addition 10 g. of formaldehyde per litre. The filaments are thereafter stretched by 150% while travelling in the air, and again by 30% in a second bath, which has the same conditions and the same temperature as the inter- 8 viscose having a viscosity of at least 400 poises, a gamma index of at least 45 and containing a cellulose having a DP of at least 500 into a spinning bath containing less than 40 g./l. of sulphuric acid, from 10 to 100 g./l. of

mediate bath, the length of immersion in this bath being 230 cm. The filaments then pass, with a length of immerf i f and less than 1 of Zmc Sulphate sion of 490 cm. through a third bath at obtained wh1le maintaining the bath at a temperature below C., by dilution of the first bath, so that it contains 6-8 g. Yvlthdrawing the filaments from the Spinning bath, m per litre of sulphuric acid, the sodium and zinc sulphates g the cess S lution from said filaments by pressure, having the same ratio of dilution, while these filaments then passing the filaments into a second cold bath havin 10 g are sub ected at the same time to a relaxation of 0.8%. h Same composition as Said Spinning bath, and than The total stretch s thus 223%.F1nally, the tow of 12,00 through a third bath containing hot dilute acid, while 1S recelved m h detensloned. State on appmpnate stretching the filaments by at least 100% at a stage prior supports. After a period of stagnation of 6 to 10 hours, to their removal fro th d b th the tow is cut into fibres in the acid state. The fibres are m e f' a then d q idifi d by washing i ft d Water they 2. The process set forth in claim 1 in which a surface are treated with a sodium hydroxide solution in a concenctive protective agent is added to the viscose. tration of 50 g./l at 30 C. for 30 minutes in the state 3. The process set forth in claim 1 in which the viscose P y Swelllng, d the P P 1S thereafter T has a viscosity of above 400 poises, a gamma index above gi the Z of nnsmg desulphunsmg 55, and the bath contains from 5 to g./l. of sulphuric was mg, 01 mg an rying.

In the second embodiment, exactly the same procedure frotm 2 fg g f and the bath is adopted as has just been indicated, except that a second empera we 15 e Ween an Stretching bath at 5 c is employed 4. The process set forth in claim 1 in which said fila- There are indicated in the following table the proper- 25 ments ar retched in air by at least 150% between said ties of the filaments obtained in embodiments 1 and 2 of intermediate bath and said second bath. this exartnple, gs c lrinpar wli 31 P P 21 ht h i g' 5. The process set forth in claim 1 in which said filaments 0 tame in xamp e an as compare W). e t h filaments obtained with a first bath at 20 C. without an S :5? Suite Fd at 1 between Sald intermediate bath containing formaldehyde: mterm late at an 531 Second at Filaments Filaments Filaments obtained Filame ts obtained according in accordobtamcdm with bath to Example ance with accordance at 20 C. One. the first with the embodiinvention ment Count, den 1.5 1.5 1- 5 5 Dry tenacity, g./den 3. 8 5. 2 5. 8 9 Wet tenacity, gJden 2.9 4. 1 4. 5 4 Dry elongation, percent..- 13 12. 3 3- 2 Wet elongation, percent 14 12. 9 l5 2 Loop tenacity (gJden) 0. 6 0 7 0 72 Modulus (wet elongation, percent under a load of 0.5 gJden.) 2. 3 l. 6 2 1 So-callcd Polynosic characteristics:

Wet tenacity after action of 5% NaOH, g./den 1.8 3.2 3 3 Modulus (wet elongation, percent %r t8'r I%l i% l .ff? 7 3. 7 3. 2 3- 2 This table distinctly shows that the filaments possess References Cited so-called Polynosic properties which are distinctly su- UNITED STATES PATENTS perior to those of the filaments obtained in accordance 2,607,955 8/1952 Drisch et alwith Example 1 and to those of the filaments obtained 2,703,270 3/1955 Studer et A with a bath at 20 C. without intermediate bath. In add1- 2,705,184 3/1955 Dri h r 1, tion, this table illustrates the fact that properties oi the 3,083,075 3/ 1963 Saxton et al. 264 197 filaments obtained in embodiment 1 of Example 5 (cold 3,108,849 0/ 1963 Owashi et al 264 197 stretching bath) are slightly superior to the properties of f the filaments obtained in embodiment 2 of Example 5 W et 264-198 h 0b h t M dt 1 3,153,687 10/1964 Eskridge 264 19 X ot stre tc m at no a y in regar o e onga ion. 3,226,461 12/1965 Wise et a1 197 X What is claimed is: 1. A process for the production of filaments of regen- FOREIGN PATENTS erated cellulose having a wet tenacity of at least 4 g./d. 915303 1/1963 Great n.

and an elongation in the wet state of less than 3% .under a load of 0.5. g./d. which comprises spinning a ALEXANDER H. BRODME'RKEL, Primary Examiner. J. WOO, Assistant Examiner. 

1. A PROCESS FOR THE PRODUCTION OF FILAMENTS OF REGENERATED CELLULOSE HAVING A WET TENACITY OF AT LEAST 4G./D. AND AN ELONGATION IN THE WET STATE OF LESS THAN 3% UNDER A LOAD OF 0.5 G./D. WHICH COMPRISES SPINNING A VISCOSE HAVING A VISCOSITY OF AT LEAST 400 POISES, A GAMMA INDEX OF AT LEAST 45 AND CONTAINING A CELLULOSE HAVING A DP OF AT LEAST 500 INTO A SPINNING BATH CONTAINING LESS THAN 40 G./L. OF SULPHURIC ACID, FROM 10 TO 100 G/L. OF SODIUM SULPHATE AND LESS THAN 1 G./L. OF ZINC SULPHATE, WHILE MAINTAINING THE BATH AT A TEMPERATURE BELOW 10*C., WITHDRAWING THE FILAMENTS FROM THE SPINNING BATH, REMOVING THE EXCESS SOLUTION FROM SAID FILAMENTS BY PRESSURE, THEN PASSING THE POSITION AS SAID SPINNING BATH, AND THEN THROUGH A THIRD BATH CONTAINING HOT DILUTE ACID, WHILE STRETCHING THE FILA- 